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Computer History Museum Makes Historic CP/M Operating System Source Code Available to the Public

Computer History Museum adds Control Program for Microcomputers as a part of its Software Historical Source Code Series

October 01, 2014 — Mountain View, Ca

The Computer History Museum (CHM) announced today that it has made available original source code for early versions of CP/M (Control Program for Microcomputers). Written by Gary Kildall to enable the transfer of data from the new floppy disk drive storage units to an Intel 8080 microprocessor-based computer, CP/M became the dominant operating system for hobbyist and small business system users in the late 1970s.

“CP/M was unlike most other operating systems in that it consumed very little memory space and could be ported to run on many different personal computers models of the era,” said Len Shustek, Museum chairman of the Board of Trustees. “Combined with its early availability and low cost, this made CP/M a runaway success and laid an important foundation for the personal computer revolution.”

The Institute of Electrical and Electronic Engineers (IEEE) has recognized the development of CP/M as an IEEE Milestone in Electrical Engineering and Computing by installing a bronze plaque outside the former headquarters of Kildall’s company, Digital Research, Inc. in Pacific Grove, California. To mark the 40th anniversary of the prototype demonstration in Kildall’s backyard tool shed in the fall of 1974, the Computer History Museum is pleased to make available, for non-commercial use, the source code of several of the early releases of CP/M.

The museum is releasing scanned printer listings and/or machine-readable source code for four early versions of CP/M dating from 1975 to 1979. These include the earliest source code for CP/M we have been able to locate, dating from before there were official version numbers. It was used at Lawrence Livermore Labs for their Octopus network system. Version 1.3 in 1976 was the first release to include the BIOS (Basic Input Output System) code that made it easy to modify the software for different computers. This includes an amazing 48-page reverse-engineered source code listing with a hand-annotated disassembly of the object code. Versions 1.4 and 2.0 allowed compilation and assembly on personal computers and considerably expanded and generalized access to disks.

"We think preserving historic source code like these programs is key to understanding how software has evolved from primitive roots to become a crucial part of our civilization,” said Shustek.

The Computer History Museum in Mountain View, California is a nonprofit organization with a four-decade history as the world’s leading institution exploring the history of computing and its ongoing impact on society. The Museum is dedicated to the preservation and celebration of computer history, and is home to the largest international collection of computing artifacts in the world, encompassing computer hardware, software, documentation, ephemera, photographs and moving images.

The Museum brings computer history to life through large-scale exhibits, an acclaimed speaker series, a dynamic website, docent-led tours and an award-winning education program. The Museum’s signature exhibition is “Revolution: The First 2000 Years of Computing,” described by USA Today as “the Valley’s answer to the Smithsonian.” Other current exhibits include “Charles Babbage's Difference Engine No. 2,” “IBM 1401 and PDP-1 Demo Labs”, and “Where To? The History of Autonomous Vehicles.”